[QUOTE=cy;13238761]just changed out a hi/lo pressure switch on a semi-hermetic compressor using this tactic. get everything ready for the switch, then crack system open. plug release port with finger, then quickly switch out fittings.

very little refrigerant lost with zero contamination getting into system because positive pressure was never lost. much less refrigerant lost vs pumping down system.
QUOTE]

CY - Why would you pump down the system? Why not just isolate the compressor instead of hoping you can change the control out fast enough. If it's a semi-hermetic it has isolation valves....just wondering.

05-19-2012, 01:14 AM

VTP99

Why would you pump down the system? Why not just isolate the compressor instead of hoping you can change the control out fast enough. If it's a semi-hermetic it has isolation valves....just wondering.[/QUOTE]

That would depend on where his pressure control lines were located.

05-19-2012, 08:16 PM

pherman

Quote:

Originally Posted by VTP99

Why would you pump down the system? Why not just isolate the compressor instead of hoping you can change the control out fast enough. If it's a semi-hermetic it has isolation valves....just wondering.

That would depend on where his pressure control lines were located.[/QUOTE]

True...but he said it was on a semi-hermetic compressor so I assumed it was on the compressor itself.

05-19-2012, 09:35 PM

VTP99

Quote:

Originally Posted by pherman

That would depend on where his pressure control lines were located.

True...but he said it was on a semi-hermetic compressor so I assumed it was on the compressor itself.[/QUOTE]

True... but unless it's a service valve with two ports (which I do see occasionally) I would add one else where. Service valves with one port and a control line attached to them are prone to leak. The packing on the stem is not very reliable left open. Most manufactures will use a two port valve or place one elsewhere. ;)

05-20-2012, 12:32 AM

pherman

True....but how come the two of us are just speculating...where's CY?

I usually see the pressure controls attached to the body of the compressor. So isolating the compressor is the way to go and the service valves are closed except for service.